A physical interface can consists of multiple logical interfaces, each called a unit. Each unit has a number as a unique identifier. The 0 just refers to the first logical interface.
If you are configuring a point-to-point circuit or non-VLAN-tagged Ethernet, the logical unit number must be zero.
Logical unit 32767 is created to accept untagged (control packets like LACP) packets that come in on an interface.
Logical interface lo0.16385 is the loopback interface for the internal routing instance. Created by the internal routing service process, this interface facilitates internal traffic. It prevents any filter created on loopback lo0.0 from blocking internal traffic.
The logical unit number can be in the range 0 through 65,535 for demux and PPPoE static interfaces only. The logical unit number can be in the range 0 through 16,385 for all other static interface types.